Obesity is a common condition and growing public health problem in developed nations including the United States. As of 2009, more than two thirds of American adults, approximately 127 million people, were either overweight or obese. Over one third of American adults are obese. Data suggest that 300,000 Americans die prematurely from obesity-related complications each year. Many children in the United States are also either overweight or obese. Hence, the overall number of overweight Americans is expected to rise in the future. It has been estimated that obesity costs the United States over $100 billion annually in direct and indirect health care expenses and in lost productivity. This trend is also apparent in many other developed nations.
For adults, the body mass index (BMI) is used to determine if one is overweight or obese. A person's BMI is calculated by multiplying body weight in pounds by 703 and then dividing the total by height in inches squared. A person's BMI is expressed as kilograms per meter squared. An adult is considered overweight if his or her BMI is between 25 and 30 kg/m2. Obesity is defined as possessing a BMI between 30 and 40 kg/m2. A BMI greater than 30 kg/m2 is associated with significant co-morbidities. Morbid obesity is defined as possessing either a body weight more than 100 pounds greater than ideal or a BMI greater than 40 kg/m2. Approximately 5% of the U.S. population meets at least one of the criteria for morbid obesity. Morbid obesity is associated with many diseases and disorders including, for example: diabetes; hypertension; heart attack; stroke; dyslipidemia; sleep apnea; pickwickian syndrome; asthma; lower back and disc disease; weight-bearing osteoarthritis of the hips, knees, ankles and feet; thrombophlebitis and pulmonary emboli; intertriginous dermatitis; urinary stress incontinence; gastroesophageal reflux disease (GERD); gallstones; and, sclerosis and carcinoma of the liver. In women, infertility, cancer of the uterus, and cancer of the breast are additionally associated with morbid obesity. Taken together, the diseases associated with morbid obesity markedly reduce the odds of attaining an average lifespan. The sequelae raise annual mortality rates in affected people by a factor of 10 or more.
Current treatments for obesity include diet, exercise, behavioral treatments, medications, surgery (open and laparoscopic), and endoscopic devices. New drug treatments for obesity are currently being evaluated in clinical trials. However, a high efficacy pharmaceutical treatment has not yet been developed. Further, short-term and long-term side effects of current pharmaceutical treatments often concern consumers, pharmaceutical providers, and/or their insurers. Generally, diet or drug therapy programs have been consistently disappointing, failing to bring about significant, sustained weight loss in the majority of morbidly obese people.
Currently, most operations used to treat morbid obesity include gastric restrictive procedures, involving the creation of a small (e.g., 15-35 ml) upper gastric pouch that drains through a small outlet (e.g., 0.75-1.2 cm), setting in motion the body's satiety mechanism. About 15% of operations used to treat morbid obesity performed in the United States involve combining a gastric restrictive procedure with a malabsorptive procedure. Typical malabsorptive procedures divide small intestinal flow into a biliary-pancreatic conduit and a food conduit. Potential long-term side effects associated with abdominal surgical procedures include herniation and small bowel obstruction. In addition, long-term problems specific to bariatric procedures also include gastric outlet obstruction, marginal ulceration, protein malnutrition, and vitamin deficiency.
Other surgical strategies for treating obesity include endoscopic procedures, many of which are still in development. Endoscopic procedures and devices to produce gastric pouch and gastrojejunal anastomosis are used to replicate laparoscopic procedures. Endoscopically placed gastric balloons restrict gastric volume and result in satiety with smaller meals. For example, U.S. patent application Ser. No. 10/221,562, now issued as U.S. Pat. No. 7,172,613 and assigned to Districlass Medical SA, describes an “intragastric device inserted by endoscopic path into a patient's stomach. The device includes a balloon or envelope having a specific nominal volume. The balloon is sealingly connected to connecting elements consisting of a disc forming a support base for the balloon against an inner wall of the stomach. The device also includes a flexible tube or catheter for connecting the balloon to a filling device and catching element integral with the tube or catheter. The connection elements enable a doctor to set and/or remove the balloon and to fix, either inside the patient's body, or subcutaneously the filling device and to be able to bring the balloon or envelope to its predetermined nominal volume.”
The silicone intragastric balloon (IGB) has been developed as a temporary aid to achieve weight loss specifically for people who weigh 40% or more of their ideal weight and who have had unsatisfactory results in their treatment of obesity, despite being cared for by a multidisciplinary team. This treatment is also indicated for morbidly obese patients who have a high morbidity and mortality risk for surgery. The placement and removal of the IGB is an endoscopic procedure and the balloon is designed to float freely inside the stomach. The IGB technique reduces the volume of the stomach and leads to a premature feeling of satiety. However, use of IGBs did not show convincing evidence of a greater weight loss. The relative risks for minor complications, for example, gastric ulcers and erosions, were significantly raised. All inflatable IGB devices suffer from the problem of deterioration of the balloon over time. This deterioration can result in deflation with loss of efficacy and complications such as small bowel obstruction secondary to balloon migration. Due to loss of efficacy over time, IGB devices are recommended only for short (<6 month) durations. In addition, rapid inflation of the balloon poses the risk of esophageal or gastric perforations, both of which are surgical emergencies. Deaths have been reported in patients using IGB treatment.
Endoscopic procedures are also used to deploy mesh structures into the stomach in an effort to occupy stomach volume and create the artificial sensation of being full. For example, U.S. patent application Ser. No. 11/657,231, assigned to Wilson-Cook Medical, Inc., describes an “intragastric device generally compris[ing] a strip digestive-resistant mesh material that is operable between a first configuration and a second configuration. The first configuration is sufficiently small to permit introduction of the digestive-resistant mesh material into a gastric lumen of the mammal. The second configuration is sufficiently large to prevent the digestive-resistant mesh material from passing through the mammal's pylorus, thereby permitting the mesh member to act as an artificial bezoar.”
Although endoscopically placed balloon structures can be effective, they are not without their associated risks and complications. Mesh structures are effective in occupying available gastric volume but they do not address gastric emptying. Migration and small bowel obstruction from such devices continue to remain a significant problem. Therefore, a need exists for an intragastric device to treat obesity that combines the benefits obtained through reducing stomach volume, slowing gastric emptying, and providing a bypass for food past the pylorus and a portion of the small intestine, while remaining relatively safe. The device should also include a component for preventing migration of the entire device out of the stomach. This device should limit side effects and be able to be deployed and removed in a non-invasive manner with relative ease. In addition, this device should have the option of further treating obesity by including the benefits obtained by malabsorptive diversion procedures. The addition of this optional benefit would make the device effective in treating not only obesity, but type II diabetes as well.
Typical metal structures cannot survive the hostile environment, particularly with respect to the high acidity, of the stomach. Intragastric devices comprising acid-sensitive components, such as metal wires, are typically covered or coated in an acid-resistant material (i.e. silicone) to prevent degradation of these components by acidic gastric contents. Conventional manufacturing processes for creating these coated intragastric devices first coat the metal wires of the device and then form the wires into the desired end shape of the device. As the shapes and structures of intragastric devices become more complicated, these conventional processes are unable to properly create the desired end product. A shape memory metal, such as Nitinol, is heat-set at temperatures in excess of 400° C. Coating the metal with an acid-resistant material and then heat-setting into the final shape would result in destruction of the coating during exposure to the high temperatures. Therefore, a method of manufacture is needed wherein the wires of the intragastric device are first formed into the desired end shape and are then coated with a corrosion-resistant material. Such a method will take care to prevent the coating and covering or clogging of the spaces or openings between the wires of the wire mesh. Such a method will also produce a finished device that is still flexible enough to be converted from a compressed, first pre-deployment shape to an expanded, post-deployment shape.
Specific surgical options for the treatment of obesity also include laparoscopic sleeve gastrectomy (LSG) and laparoscopic roux-en-y-gastric bypass (RGB) surgery. Gastrectomy refers to a partial or full surgical removal of the stomach. LSG is a restrictive treatment, surgical weight-loss procedure in which the stomach is reduced to approximately 25% of its original size by surgical removal of a large portion following the major curve. The open edges are then attached together (often with surgical staples) to form a sleeve or tube with a banana shape. The procedure permanently reduces the size of the stomach. The procedure is performed laparoscopically and is not reversible. Following the operation, the stomach empties its contents rapidly into the small intestine, but with little or no vomiting (characteristic of other restrictive procedures).
LSG involves a longitudinal resection of the stomach on the greater curvature from the antrum starting opposite the nerve of Latarjet up to the angle of His. The first step of the procedure is the division of the vascular supply of the greater curvature of the stomach which is achieved with the section of the gastro-colic and gastro-splenic ligaments close to the stomach. The greater curvature is completely freed up to the left crus of the diaphragm to resect the gastric fundus that harbors the ghrelin secreting cells of the stomach. The second step of the procedure is the longitudinal gastrectomy that “sleeves” the stomach to reduce its shape to a narrow tube. The pylorus and part of the antrum are preserved, resulting in a lesser curvature-based “restrictive” gastric sleeve.
Sleeve gastrectomy (also called gastric sleeve) is usually performed on extremely obese patients, with a body mass index of 40 or more, where the risk of performing a gastric bypass or duodenal switch procedure may be too large. A two-stage procedure is performed: the first is a sleeve gastrectomy; the second is a conversion into a gastric bypass or duodenal switch. Patients usually lose a large quantity of their excess weight after the first sleeve gastrectomy procedure but, if weight loss ceases, the second step is performed.
For patients that are obese but not extremely obese, sleeve gastrectomy alone is a suitable operation with minimal risks. The sleeve gastrectomy is currently an acceptable weight loss surgery option for obese patients as a single procedure. Most surgeons prefer to use a bougie (tapering cylindrical instrument) having an outer diameter between 32-60 French (the optimal bougie size is 32 Fr-36 Fr) with the procedure. The ideal approximate remaining capacity of the stomach after the procedure is 15 ml.
One of the mechanisms involved in weight loss observed after the LSG is the dramatic reduction of the capacity of the stomach. The concept of restriction has been widely used in bariatric surgery in vertical banded gastroplasty (VBG) and laparoscopic adjustable gastric banding (LAGB). The distension of the small gastric pouch in the LAGB procedure or VBG is intended to account for the feeling of early fullness, enhanced satiety and decreased hunger experienced by a patient after the ingestion of small quantities of food.
The hormonal modifications induced by LSG differ from those found after a purely restrictive procedure such as LAGB. Ghrelin, a peptide hormone mainly produced in the fundus of the stomach, is believed to be involved in the mechanisms regulating hunger. There is a significant reduction in ghrelin associated with resection of the gastric fundus.
What makes LSG a preferable option lies in the fact that the operation is a straightforward procedure that can generally be completed laparoscopically, even in the case of an extremely obese patient. It does not involve any digestive anastomosis and no mesenteric defects are created, eliminating the risk of internal hernia. In addition, no foreign material is used as in the case of gastric banding, the whole digestive tract remains accessible to endoscopy, and it is not associated with Dumping syndrome. Also, the risk of peptic ulcer is low and the absorption of nutrients, vitamins, minerals and drugs is not altered.
Early reports of LSG have shown it to be safe and effective with marked weight loss and significant reduction of major obesity-related comorbidities. The question whether LSG may work as a sole bariatric procedure in the long term cannot yet be answered. For this reason, LSG is proposed as the first step of a staged approach in patients for whom a biliopancreatic diversion with duodenal switch (BPD-DS) or RGB seems too hazardous because of a very high BMI (super obesity=BMI>50 or super-super obesity=BMI>60) and/or associated diseases whether related or not to obesity.
Laparoscopic roux-en-y-gastric bypass (RGB) involves the creation of a small (20-30 ml) gastric pouch and a Roux limb (typically 75-105 cm) that reroutes a portion of the alimentary tract to bypass the distal stomach and proximal small bowel. Following RGB, a pleiotropic endocrine response may contribute to improved glycemic control, appetite reduction, and long-term changes in body weight. RGB also has a profoundly positive impact on obesity-related comorbidities and quality of life. Other advantages include established long-term effectiveness for sustained weight loss, reduction of comorbidities, minimal risk for long-term nutritional sequelae, and effective relief of gastroesophageal reflux disease (GERD). RGB is not without risks. Common causes of death include pulmonary embolism and anastomotic leaks. Nonfatal perioperative complications include anastomotic leaks, venous thromboembolism, wound infections, small bowel obstruction, and bleeding. Postoperative gastrointestinal complications include nausea and vomiting, micronutrient deficiencies, and possible weight regain.
Failures after these bariatric procedures are common and patients start regaining weight or the progressive weight loss stops at a sub-therapeutic level. Therefore, there is a need for salvage therapy after one or more failed bariatric procedures. What is needed is a device to be used following bariatric surgery that will combine the benefits of gastric volume reduction, bilio-pancreatic diversion and/or intestinal bypass to enhance the weight loss effects of the device. What is also needed is a device that will further reduce the volume of a surgically restricted stomach to reduce the amount of calories that can be consumed. The device will also bypass the proximal small intestine or the roux limb of the intestine in order to produce intestinal mal absorption, bilio-pancreatic diversion or both. The device can further act to delay gastric emptying, release the gastric hormones associated with satiety, and stimulate the gastric nerves associated with sensation of satiety. The device could be combined with other therapeutic agents such as electrical stimulation, magnetic stimulation, or pharmaceutical agents.
The device can be used as a primary therapeutic procedure for weight loss or as a bridge to surgery for a definitive weight loss procedure. The device may also be used in the treatment of other conditions including, but not limited to, metabolic syndrome, diabetes mellitus, dyslipidemias and cardiovascular disease.